A(5,9)＝15120-搜答案-大师作文网

a²+a+5＝7a²+a-2=0(a-1)(a+2)=0a=1或a=-23a²+9a-2=3×1²+9×1-2=10或3a²+9a-2=3×（-2）&

=【2（a-5）/（a-3）²】*【1/(a+5)(a-5)】+【15a/5-a】=【2/(a-3)²*（a+5）3a²】+【15a/5-a】再通下分就好了.再问：通分后

解(3a-2a²)-[5a-1/3(6a²-9a)-4a²]=3a-2a²-[5a-2a²+3a-4a²]=3a-2a²-(8a-

把后面那个a^2-9拆分成（a-3)(a+3),再乘进去就是（3a(a-3)(a+3)/（a-3)a -a(a-3)(a+3)/(a+3)a)化简后就是2a+12 &n

因为a*b=2×a+b，所以：a*2a=2a+2a=4a，4a*3a=4a×2+3a=11a，11a*4a=11a×2+4a=26a，26a*5a=26a×2+5a=57a，57a*6a=57a×2+

a=1/(√5+2)=(√5-2)/(√5+2)(√5-2)=(√5-2)/(5-4)=√5-22

原式=(a+2)(a-2)/(a+3)²×2(a+3)/(a-2)=(a+2)/(a+3)=(-5+2)/(-5+3)=3/2

原式=-4a²-(5a-8a²-6a²+3a+9a²)=-4a²-(8a-5a²)=-4a²-8a+5a²=a²

[(a+3)/(a^2-4)+a/(6-a-a^2)]除以(4a+9)/(5a-10)先化简=[(a+3)/(a+2)(a-2)]-a/(a+3)(a-2)除以(4a+9)/(5a-10)通分（a+2

15a^2-{-4a^2+[5a-8a^2-(2a^2-a)+9a^2]-3a}=15a^2-{-4a^2+[5a-8a^2-2a^2+a+9a^2]-3a}=15a^2-{-4a^2+[6a-a^2

1+2a+3a^2+4a^3+5a^4+6a^5+5a^6+4a^7+3a^8+2a^9+a^10=(1+a+a^2+a^3+a^4+a^5)+a(1+a+a^2+a^3+a^4+a^5)+a^2(1

(a-4)/(a^2-9)除以1/(a-3)乘以(a^2+2a-3)/(a^2-8a+16)=(a-4)(a-3)(a-1)(a+3)/[(a+3)(a-3)(a-4)²]=(a-1)/(a

a2a3a4a5a=(2a+2a)3a4a5a=8a+3a4a5a=22a+4a5a=52a+5a=57a=114a=2

15a²-【5a-8a²-（2a²-a）+9a²】=15a²-[5a+a²-2a²+a]=15a²-6a+a²

4a-9与3a-5互为相反数4a-9+3a-5=0a=2a*a-2a+1=2*2-2*2+1=1

本题难度是在下标和第n项的关系,但是分步求可以实现设等比数列{xn}的公比为a(a不等于0),x1=1,前n项和为Xn,则：xn=a^(n-1)Xn=(1-a^n)/(1-a)令原式和为S,则S=X1

原式=a+(3a-2a)+(5a-4a)+……+(2009a-2008a)=a+a+a+……+a=1005a

2/9-3a=2/3（3-a)=-2/3(a-3)a-1/a²-3-2a=(a-1)/(a+1)(a-3)a/a²-5a+6=a/(a-2)(a-3)对比可发现最小公分母为：3（a

先化简分子2a^5+3a^4+3a^3+9a^2-5a+1=(2a^5+3a^4-a^3)+(4a^3+6a^2-2a)+(3a^2-3a+1)=a^3(2a^2+3a-1)+2a(2a^2+3a-1